Apparatus for producing electric sparks for use in spectrum analysis



July 1940- H. KAISER 2.209.523 APPARATQS FOR PRODUCING ELECTRIC SPARKS FOR USE IN SPECTRUM ANALYSIS Filed April 8, 1939 Invenfor:

" Mm My,

Patented July 30, 1940 UNITED STATES PATENT OFFICE APPARATUS FOR PRODUCING ELECTRIC SPARKS FOR USE IN SPECTRUM ANALY- SIS Heinrich Kaiser, Jena, Germany, assignor to the firm of Carl Zeiss, Jena, Germany In Germany April 11, 1938 6 Claims. (Cl. 176-8) The present invention concerns apparatus for producing sparks in spectrum analysis, which have a plurality of spark gaps connected in series to each other and to an energy accumulator to 5 be discharged. Apparatus of this kind play an important part in spectro-analytic tests of materials. In a known embodiment of a spark producer, one spark gap, the electrodes of which are constituted by specimens of the material to be examined, is connected in series to the two spark gaps of a rotary interrupter. Other embodiments are known which have two series-connected spark gaps and in which the spectral lines of the one spark gap are compared to those of the other. To obtain an unobjectionable working 01 these known apparatus, it is necessary to provide that the series-connected gaps spark over simultaneously or successively at very short intervals (of for instance 10- to 10- seconds). It is neces- 20 sary, therefore, that, at all gaps, the necessary sparking voltage is arrived at nearly simultaneously and that, moreover, all gaps have at the same time the electrons for starting the sparking. If not, it may happen that sparking takes place 25 in the one gap and the discharge is then interrupted on account of the next gap not being conductive as yet. The sparks are thus m'adeto flicker, and they start at irregular intervals and occasionally not at all, even when use ismacle so of the known mechanical control by means of interrupters in the form 'of rotary spark gaps. This difllculty has generally been overcome so far by radiating the spark gapswith ultra-violet rays or aradium preparation. 'I'hismethod is,

35 however, restricted in effectiveness and naturally adds to the cost of the entire apparatus. Ensuringa reliable sparking in the gaps by means of very high voltages is rather expensive as well.

It has also been taken into consideration that 40 the charging voltage of the energy accumulator,

which produces the sparking in the gaps, is apportioned to .these gaps inversely to their capacities. The high-capacity spark gaps receive, accordingly, only a small portion of the charging 45 voltage, so that the breakdown field-strength is eventually not arrived at.

The invention provides that in. apparatus for producing single sparks or series of sparks and having a plurality of spark gaps connected in 5 series and traversed by thesame discharge current. at. least part of these gaps is bridged by conducting means. For bridging, use can be made either of resistances, condensers or choking coils producing an impedance of approximately $8 10-- to 10" ohms. or of a plurality of such eiecharging voltage for a long time.

ments connected in series or in parallel. It is preferable, however, to use a high ohmic resistance producing the said impedance. The most convenient method consists -in bridging, if possible all spark gaps except one by reaetances, so that nearly the entire charging voltage is at this one unbridged spark gap. When a sparking has taken place in this one gap, the discharge cannot be interrupted, because a weak discharge current can flow through the bridging resistances of the other spark gaps. After the sparking,,the voltage decreases at the unbridged spark gap down to glow voltage (some 100' volts) and eventually to are voltage (some 10 volts). At this moment,

nearly the, entire charging voltage (some 1,000 volts) is at the spark gaps bridged by the resistances, so that the sparking voltage of these gaps can be arrived at by giving these resistances the correspond ng value. If the apparatus has only one spark (gap bridged by a resistance, the magnitude of the resistance can be varied within wide limits. If a plurality of bridged spark gaps are connected in series, the bridging reactances can be different y great and so graduated that the greater part of the charging voltage arises at the spark gap altering the higher resistance and, after the sparking in this gap, arrives at the next' lower resistance. accordingly, the sparking voltage is, so to say, made to travel from spark gap to spark gap.

The apparatus embodying the invention accordingly serves two ends:

1. The distribution of potentials at the seriesconnected spark gaps is so controlled that the greater part of the charging voltage lies first at the unbridged gap or gaps and is passed on to the other gaps only subsequentlyv to having sparked in the unbridged gap or gaps.

2. Sparking in the entire series of gaps no longer depends on the haphazard presence oi 40 initiating electrons at each one of the gaps at the same time.

Bymaking a mistake in operating the appara: tus, for instance by using too great a spark length or, in other words, by givingthe electrodes too great a distance apart, so that sparking is prevented, a damaging oi the bridging reactances may occur. Upon an interruption in sparking these reactances are caused to stand the entire This disadvantage can be overcome by disposing parallel to the bridging reactances protective spark gaps or automatic circuit breakers, for instance heat switches.

The sparking voltage at a gap is high as long of the charging voltage in the ordinary service. According to the invention it is also possible,

however, to provide that the spark gaps connected in series are first short-circuited and then opened one after the other, so that the normal charging voltage sufiices for producing reliable successive sparkingsof the series-connected gaps.

.In the spectrum analysis of metals, it has proved to be advisable to produce on the surfaces of the electrodes constituted by the metals an electric equilibrium some time before the analysis proper by effecting preliminary spark discharges. The period necessarily elapsing between these preliminary spark discharges and parallel to the impedances I3 and I4.

the practical use of the arrangement entails an undesired delay of the spectrum analysis. The preliminary spark discharges between one pair of electrodes can take place, however, at the same time as the spectrum analysis by means of another pair of electrodes, if at least two oi the spark gaps can be used for spectrum analyses. Accordingly, while the one of these gaps is being used for spectra-analytical tests, the other can be made ready, and vice versa.

The accompanying drawing shows diagram-' matically an example of a wiring diagram of the apparatus used for spectrum analysis according to the invention.

Two terminals I and 2 are assumed to be corinected to a source of alternating current of 50 periods. -To these terminals are connected a regulating resistance 3 and the primary winding 4 of a high-voltage transformer 5 supplying the charging voltage. Parallel to the secondary winding 6 of this transformer 5 is a spark circuit,

which comprises an accumulating condenser I, a

choking coil 8 and spark gaps 9 to I2 in series with these elements, the spark gaps 9 I0 and I I being analyzer gaps and I2 a rotary/interrupted. The electrodes 9, II] and II consist of the alloy or mixture of elements or compounds thereof, of which the percentage of quantity of the respective elements is to be analised. I3 is a high ohmic resistance parallel to I0, and I4 a condenser parallel to II. I5 and I6 are safety spark gaps lengths of the gaps I5 and I6 are greater than those of thegaps I0 and II, these greater spark lengths preventing an overloading of the impedances I3 and. short-circuiting the series of spark gaps over the contacts I8, I9 and 20 and permitting a successive opening of the spark gaps.

The device is operated by connecting a source of alternating current of say 50 periods between the terminals I and,2 and by rotating the rotary The "spark I1 is a knife-switch for interrupter I2. The knife-switch II is at first in the position of shortcircuiting the series of spark gaps. the shortcircuits of the spark gaps are removed successively and the sparks will be ignited one after the other during each ignition of the rotary interrupter I2. Then the knife-switch will remain opened during the entire sparking period.

I claim:

1. A device for producing electric sparks for use in spectrum analysis, comprising a high voltage source, an energy accumulator connected to said source, a plurality of spark gaps connected in series to said energy accumulator for discharging said accumulator, and impedances bridging part of said spark gaps.

2. A device for producing electric sparks for use in spectrum analysis, comprising a high voltage'source, an energy accumulator connected to said source, a plurality of spark gaps connected in series to said energy accumulator for discharging said accumulator, and impedances comprising high ohmic resistances bridging part of said spark gaps.

3. A device for producing electric sparks for use in spectrum analysis, comprising a high voltage source, an energy accumulator connected to said source, a plurality of spark gaps connected in series to said energy accumulator for discharging said accumulator, and impedances bridging all of said spark gaps except one.

4. A' device for producing electric sparks for use .in spectrum analysis, comprising a high voltage 'source, an energy accumulator connected to said source, a plurality of spark gaps connected in 'series to said energy accumulator for discharging said accumulator, and impedances bridging part of said spark gaps, the impedances bridging each one of said bridged spark gaps being graduated in value with respect to the values of the impedances bridging each of the other spark gaps in order to obtain the greater part of the said high voltage of said energy accumulator at the spark gap offering the higher resistance, so that sparking over takes place in series in all said spark .gaps.

5. A device for producing electric sparks for use in spectrum analysis, comprising a high voltage source, an energy accumulator connected to said source, a plurality of spark gaps connected in series to said energy accumulator for discharging said accumulator, impedances bridging part of said spark gaps means for short-circuiting said spark gaps and means for connecting them successively to the series circuit at the beginning of a series of sparks.

6. A device for producing electric sparks for use in spectrum analysis, comprising a high voltage source, an energy accumulator connected to said source, a plurality of spark gaps connected in series to said energy accumulator for discharging said accumulator, impedances bridging part of said spark gaps, and safetyspark gaps connected in parallel to said impedances for preventing an overloading of said impedances.

' HEINRICH KAISER.

Then this switch is opened so that 

